Internal migration
Internal migration refers to human migration within one geopolitical entity, usually a nation. Reasons for internal migration tend to be different from those for cross-border migration; whereas the latter often occurs primarily for political or economic reasons, reasons for internal migration prominently include travel for education and for economic, but not for political, reasons. A general trend of movement from rural to urban areas has also produced a form of internal migration, leading to rapid urbanization in many countries.
The history of many countries has seen massive internal migration:
The United States saw a massive internal migration from the eastern states toward the west coast during the mid-19th century, a similar large-scale migration of African Americans from the agricultural south to the industrialized northeast in the early to mid-twentieth century, and a large-scale reverse migration of African Americans from other parts of the country to the urban south beginning in the late 20th century and continuing to the present.